Eruption of the Permanent First Premolar Associated with a Mandibular Keratocystic Odontogenic Tumor after Marsupialization in a 9-year-old Boy: A Case Report with 2 years of follow-up

Amongst odontogenic cysts, keratocystic odontogenic tumor (KOT) is a benign intra-osseous lesion, characterized by corrugated parakeratinized uniform stratified squamous epithelium, with potential for aggressive behavior and high tendency to recur. There are multiple treatment modalities for this cyst. Some surgeons prefer the conservative treatments such as marsupialization while the others prefer invasive treatments such as radical resection. The aim of this study was to present a case of KOT involving the right mandibular premolar area with an impacted tooth in a 9-year-old boy treated by marsupialization. The treatment resulted in eruption of the mandibular first premolar, and no signs of recurrence were observed after two years. Marsupialization was found to be an effective treatment in inducing the eruption of mandibular premolar associated with KOT in preadolescents and can be a reliable procedure to reduce recurrence tendency of KOT


Introduction
In 1956, the word odontogenic keratocyst (OKC) was originally named by Phillipsen until it was classified as keratocystic odontogenic tumor (KOT) by WHO in 2005 [1].Without considering which term is used, there are three main reasons making this lesion so important: more growth potential than other odontogenic cysts, higher recurrence rate and conceivable relationship with nevoid basal cell carcinoma [2]. Besides, this odontogenic tumor is a benign intra-osseous, uni-or multicystic lesion which tends to be aggressive and infiltrative [3].
KOTs are more prevalently seen in the posterior region of the mandible than in maxilla [4]. This lesion usually manifests during the second, third or fourth decades of life with a slightly higher occurrence amongst male [5]. In approximately half of the patients, KOT is asymptomatic while in others, pain, swelling, drainage, tooth mobility or displacement and bone expansion can be seen [4,6]. The recurrence of KOT varies 5-62% [7].
In radiograph images, KOT is a uni-or multi-locular well-defined radiolucent cyst, bounded by smooth or scalloped margins and sclerotic borders [5]. Association with at least one unerupted tooth can be seen in 30% of the cases, especially in younger patients [8].
In histological examination, KOTs are characterized by a fibrous wall, lined with corrugated parakeratinized stratified squamous epithelium of 6-10 cell layers in thickness without rete pegs, which makes a flat interface between the epithelium and the connective tissue [6][7]9]. The well-defined basal layer contains palisaded columnar or cuboidal cells with higher mitotic activity than other dentigerous cysts [8]. Although the KOT treatment remains controversial, it is commonly classified as either conservative or aggressive. The conservative treatment involves "simple enucleation, with or without curettage, or marsupialization", whereas the aggressive one involves chemical curettage, peripheral ostectomy, and resection. The treatment of choice should be based on the lowest risk of recurrence and morbidity [4].

Discussion
Various approaches are utilized to treat KOTs. The conservative treatments for KOTs are marsupialization (possibly followed by residual cystectomy) and decom-  pression. The invasive treatments are resection, peripheral osteotomy, and enucleation (possibly followed by chemical agents like Corney's solution). Due to high recurrence of KOTs, the best treatment plan is still controversial [5,10]. It has been noted that treatment of choice should be based on the lowest risk of recurrence and morbidity [4]. Pogrel [11] concluded that decompression or marsupialization can preserve more vital structures and has the same success rate as the more aggressive treatments. Marsupialization is to convert the cyst into a pouch. Mandibular cysts are marsupialized into the oral cavity while maxillary cysts can be exposed into the maxillary sinus and nasal cavity as well as oral cavity [11]. In another study by Pogrel [12], it was discussed that by marsupialization, parakeratinized KOTs might get resolved completely and the teeth with-in the cyst can become upright and erupt. However, the recurrence rate should not be the only factor when choosing a treatment plan. In preadolescents, it is possible that the associated teeth would erupt spontaneously after marsupialization, according to the age and depth of the associated teeth [13]. According to Oh et al. [14], marsupialization led to obvious change in epithelium, which was no longer similar to the appearance of KOT. Their study also proved that "bone formation was significantly enhanced in the KOT capsule wall adjacent to bone after marsupialization." A recent study [15]   The authors [15] claimed that decompression as an efficient treatment of KOTs can reduce its recurrence rate. It was also mentioned that due to a few differences between marsupialization and decompression, the term marsupialization was unified with decompression.
A written informed consent was obtained from patient's parents.

Conclusion
In our case study, marsupialization was found to be an effective treatment in inducing the eruption of mandibular premolar associated with KOT in preadolescent. It seems that this treatment modality can be a reliable procedure to reduce recurrence tendency of KOT.